Deionization of a gas discharge device by varying the tube parameters



DEIONIZATION OF A GAS DISCHARGE DEVICE BY Marc-1125,1969 .QJACOBSEN 3,435,287

VARYING THE TUBE PARAMETERS Fllec April 14, 1966 Sheet /v or 2 .INVENTOR. C44: unaos :5

Max-ch25, 1969 c. JACO'BSEN DEIONIZATIQN OF A GAS DISCHARGE BY VARYING THE TUBE PARAMETER Filed April 14, 1966 INVENTOR. C445 s/flCoBgg United States Patent US. Cl. 315-110 7 Claims ABSTRACT OF THE DISCLOSURE An electric circuit making device comprises a series connection of a circuit breaker or isolating switch and a current regulating gaseous discharge valve. In this valve a normal low voltage are can be maintained only if the relationship R-n A exists, where R is proportional to the efiective area of discharge, n1 is the density of neutral atoms in the gas, and A is a parameter which depends on the type of neutral atoms in the gas. The gas discharge valve is provided for means for regulating at least one of the parameters in the inequality in such a direction that the discharge in the valve changes over from plasma condition with low arc voltage drops to space charge condition with higher arc voltage drop, and the circuit breaker or isolating switch is provided with means for opening it as soon as the current through the discharge valve is depressed due to the high voltage drop in the valve.

When it is desirable the use are discharge phenomena for breaking A.C. circuits the main idea, whether it is a question of a vacuum or high pressure arc, is to try to increase the losses of the are so that the energy loss per unit of time in the arc during the time when the current is zero is so great compared with the total energy content of the are that the remaining energy in the arc when the voltage has changed polarity is so low that it is not suflicient to generate a new cathode spot on the electrode which, before the moment when the current became zero, was the anode. With high pressure breakers this is carried out for example by blasting with compressed air. In a vacuum arc the loss speed is normally so high due to large free average path lengths that the discharge is selfquenching. I

In DC. circuit breakers attempts have been made to solve the problem along the same lines, but unfortunately it has not been possible to produce constructions with particularly great quenching properties. Existing constructions only work with high pressure and forced energy loss.

The present invention relates to a circuit breaker device which can be used for breaking direct current as well as alternating current. It consists of a conventional breaker or isolating circuit breaker in series with a cur-' rent regulating, preferably cylindrical gas discharge valve for which a normal low voltage are can be maintained only if the condition R-n A is obtained, where R is the effective radius of the valve, n the density of neutral atoms in the gas and A is a parameter which depends on the type of neutral atoms in the gas and possibly a magnetic field. The invention is characterised in that the gas discharge valve is provided with means for regulating at least one of the parameters in the non-equation R nA in such a direction that the discharge in the valve goes over from plasma condition with low arc voltage drop to space condition with high voltage drop or vice versa.

On the accompanying drawing FIG. 1 shows the principle of construction of the device, while FIGS. 2-5 show several difierent embodiments of the gas discharge valve in the device.

For a low pressure are discharge the low axial electrical field strength of the positive column depends on the plasma condition being maintained everywhere. The permanent loss of ion-electron pairs to the wall is balanced by a corresponding new generation of charged particles in the volume.

It can be shown that, for a normal low pressure discharge in a straight cylindrical valve, an independent discharge can exist only if the condition R-n A is obtained. Here R denotes the eifective radius of the discharge valve, n is the density of neutral atoms in the gas and A is a parameter which depends on the type of neutral atoms and a possible magnetic field.

In the application of the above given condition to a breaker for direct current, several procedures are possible.

The discharge is allowed to operate in the area R-n A, but the generating mechanism is influenced by further means so that the loss speed of the ion-electron pairs is lower than normal. This can be carried out for example by an outer magnetic field. By this means equilibrium can also be maintained in an area where it is not normally possible. By varying the outer magnetic field the discharge can be made to go from plasma condition with low arc voltage drop to space charge condition with high are voltage drop, after which quenching of the arc can be effected by a conventional breaker.

According to a second procedure the discharge is started within the area R-n A and then the generating speed is reducedlocally or generally so that it falls below the loss speed and the same process as described above is obtained. The said reduction can be carried out by locally or generally bringing the discharge conditions to fall below the limit R-n=A.

By low arc voltage drop we mean approximately 50 v., while high are voltage drop means around kv. at 0.1 a./cm. per one metre length of the arc.

In FIG. 1 the general device of the discharge valve is shown as well as the breaker Bs connected in series to it, which breaker can be a conventional breaker or an isolating circuit breaker. Parallel to the discharge valve a sec- 0nd breaker Bp is connected. During normal operation this breaker is closed and thus the discharge valve is short circuited.

The embodiment of the discharge valve according to the invention shown in FIG. 2 comprises a casing 1 in which in a known way an anode 2 and a cathode 3 are arranged. Around the casing there is a magnetising winding 4 which generates an axial magnetic flux passing through the casing when the winding is traversed by the magnetising current. The magnetising current source is here shown schematically as a battery 5 which is connected to a resistor 6. The magnetising winding is connected between the device one end 7 of the resistor and a movable contact 8. With the schematically shown the magnetising current and thus also the magnetic flux passing through the discharge tube can be regulated from zero to a maximum value. The magnetic field reduces the value on the parameter A. If therefore the product R-n is suitably chosen it is possible to alter the impedance of the discharge from low to high value by allowing the magnetic field to vary from a high value to Zero. Of course any suitable magnetising current source with control means can be used.

In the modification of the discharge valve shown in FIG. 3 the casing is provided with a number of bulges .10 which can extend round the casing or only around a part of the casing. Inside the bulges discs 11 are arranged which can be shaped like diaphragms of a camera so that they can be displaced out of the bulges and thereby reduce the effective radius R of the casing. When the discs are completely inside the bulges R is greatest. Then R-n A and the arc burns with low voltage drop. If R is changed by the discs being moved towards the centre of the valve so that the effective radius of the valve is reduced, the discharge will go over to space charge condition when R-n A. The are voltage drop then rises to a very high value and this means that the current through the valve falls to such a low value that the lbreaker Bs connected in series with the valve can break the circuit.

In the performance of the circuit breaker device shown in FIG. 4 the discharge valve 1 is provided with a gas inlet 15 with a gas valve 16. Further a vacuum pump 17 is connected to the valve through a vacuum valve 18. The breaker Bp connected in parallel with the valve 1 is normally closed so that the valve is short circuited. A small gas current goes continually from the gas valve 16 through the discharge valve to the vacuum pump 17 through the partly closed vacuum valve 18. By this means such a large gas pressure is maintained in the discharge valve that the condition R-n A, i.e. the number of neutral gas atoms is so great that a normal low voltage discharge are can be maitnained through the tube 1.

When breaking is to be carried out, the breaker Bp is opened and through the increased voltage over the valve 1 a discharge is ignited through this with a considerably smaller arc voltage than the voltage of the are over the breaker Bp. Thereby the current will be moved from the breaker Bp to the valve. When the breaking distance in Bp is completely de-ionised, the gas valve 16 is completely closed and the vacuum valve 18 is opened. The pressure in the tube .1 falls quickly so that the number of neutral gas atoms falls so that the condition R'n A is obtained and the discharge in the tube goes over to a space charge current with high are voltage drop. The current is by this means limited so strongly that the breaker Bs connected in series with the valve can break the current.

According to another breaking method the gas valve 16 is closed and the vacuum valve is completely open. When breaking is to be carried out the breaker Bp is opened and by its arc voltage the discharge is ignited through the valve 1 when the gas valve 16 is opened and a certain quantity of gas is let into the valve. This quantity of gas shall be so great that the discharge can ignite and burn as long as necessary in order that the breaker shall be completely de-ionised. When this has been carried out the gas valve is closed and the pressure falls quickly so that the condition R-n A is obtained and the space charge limited current is produced. Possibly a sufficiently large quantity of gas can be let in at a single short opening of the valve, i.e. that the gas valve is closed before the breaker is completely de-ionised.

The embodiment of the invention shown in FIG. has a large vacuum container 19 placed below the discharge valve. Normally the complete system is evacuated with a relatively small vacuum pump 20. When the arc discharge at a breaking of the current circuit is to be ignited a certain quantity of gas is allowed in through the gas valve 16'. The gas is accelerated downwards in the tube by the difference in pressure in the tube. When the gas front has reached the cathode the discharge is ignited assuming that the breaker has a sufficiently high are voltage. The gas continues to expand into the vacuum container and the pressure in the valve falls still more. If the ratio between the quantity of gas let into the container, the volume of the discharge valve and the volume of the container 19 is correct, the condition R-n A will be obtained in the discharge valve before the pressure is equalized in the complete vacuum system and before any gas has had time to be pumped out by the vacuum pump. One of the greatest advantages with this system is that the vacuum pump can be small but that nevertheless the characteristics of a large pump are produced by the vacuum system having a relatively great volume.

During normal conditions both the breakers Bp and Rs are closed. During breaking the current circuit the discharge valve is adjusted so that the condition R-n A is obtained. This is carried out in the variation of the invention shown in FIG. 2 by a strong magnetic field being exerted on the valve by means of the magnetic means 4 and at the device according to FIG. 3 by the discs 11 being adjusted so that the valve has its greatest effective diameter. After this the breaker Bp is opened which means that the valve ignites and a low voltage are is obtained in the valve. By reducing the magnetic flux to zero in the device according to FIG. 2 and by displacing the discs 11 in the valve in the device according to FIG. 3, the discharge goes over from plasma condition to space charge condition so that the arc resistance increases to a very high value and as a consequence of this the current is reduced to such a low value that the breaker Ex is capable of breaking the circuit definitely.

The breaking device according to the invention can be made so that it can be used for alternating current as well as for direct current. The embodiment shown in FIG. 2 can also be made so that it can be used for inverters as well as for rectifiers by the discharge being simply and quickly regulated between plasma and space charge condition.

The embodiments of the invention shown and described are only intended as individual examples of how the invention can be given a practical embodiment and many modifications are feasible within the scope of the invention.

What is claimed is:

1. An electric circuit breaking device comprising a series connection of a circuit breaker or isolating switch and a current regulating gas discharge valve, in which a normal low voltage arc can be maintained only if the relationship R-n. A exists, where R is proportional to the effective area of the discharge, n is the density of neutral atoms in the gas and A is a parameter, which depends on the type of neutral atoms in the gas, characterized in that the gas discharge valve is provided with means for regulating at least one of the parameters in the non-equal relationship R-nZA in such a direction that the discharge in the valve changes over from plasma condition with low arc voltage drop to space charge condition with high are voltage drop and that said circuit breaker or isolating switch is provided with means for opening it as soon as the current through the discharge valve is depressed due to the high voltage drop in the valve.

2. A device according to claim 1, in which said current regulating means comprises a magnetic device which can generate a longitudinal magnetic field in the valve of such a size and direction that the parameter A will be greater than the product R-n.

3. A device according to claim 1, in which said current regulating means is provided with at least one variable diaphragm for reducing the effective radius R of the value so that the product R-n falls below the value A.

4. A device according to claim 1, in which the discharge valve is connected in parallel with a circuit breaker which is normally closed.

5. A device according to claim 1, in which said regulating means comprises means for altering the pressure in the gas, so that the number of neutral atoms in the gas is altered.

6. A device according to claim 5, in which said regulating means comprises means with a gas inlet controlled by References Cited UNITED STATES PATENTS Capart 315-62 X Smith 313-161 X Stoddard 317-11 Lee 313-148 X Coleman 313-161 JAMES W. LAWRENCE, Primary Examiner.

C. R. CAMPBELL, Assistant Examiner.

US. Cl. X.R.

vBrueckner 317-11 X 15 313-7, 175, 161; 315-340, 344, 362; 317-11, 73 

